Interferon was firstly found as a material produced by living cells for inhibiting growth of virus. Since then, various studies on activities of interferon have been done and it has become clear that interferon has various aspects of biological activities. Further, according to recent technical progress, a large scale production of interferon derived from human cells or human interferon gene-recombining microbial cells and purification thereof for clinical application have become possible. Therefore, clinical application of human interferon in treatment of herpetic keratitis, hepatitis B, viral verruca, brain tumor, skin melanoma and the like has been promoted.
However interferon is a fairly unstable material. Particularly, purified clinically applicable human interferon readily decreases its activity and is readily inactivated by an elevated temperature or mechanical pressure. Accordingly, clinical application of interferon is mainly performed by using lyophilized human interferon and reconstituting it with physiological saline, distilled water or the like to form an injection solution or eye drop when it is administrated.
In order to obtain a stable interferon-containing pharmaceutical composition, various attempts have been done in the prior art. For example, International Application No. WO 83/01198 (PCT/DK82/00092) discloses an interferon-containing gel composition suitable for topical application which includes a polyhydric sugar alcohol, carboxymethyl cellulose, human albumin and a phosphate buffer and a method for treating a human patient suffering from interferon-susceptible disorders such as pre-cancerous or cancerous tumors or local virus infections such as Herpes simplex virus infections or other disorders such as dermatitis, e.g. seborrhea, etc.
Japanese Patent Laid Open Publication No. 92619/1983 discloses that a stable pharmaceutical composition suitable for topical application containing as an active ingredient interferon can be prepared by incorporating interferon with a trihydric or higher polyhydric sugar alcohol and an organic acid buffer. This Publication generically discloses that the composition is effective for treating viral diseases.
Japanese Patent Laid Open Publication No. 167520/1983 discloses that an anionic surfactant can be used as a stabilizer in an interferon-containing composition. This Publication also generically discloses that the composition is effective for treating viral diseases.
The present inventors have surprisingly found that topical or local application of an interferon-containing composition such as that disclosed in the above Japanese Patent Laid Open Publications is effective for treatment of a human subject suffering from keratosic disorders of skin and mucosa such as lichen planus and leukoplakia.
Since causes of keratosic disorders of skin and mucosa are unknown, treatment thereof is performed by, for example, administrating vitamins, adrenal cortex steroids and the like. However, such a conventional method for treating the disorders is insufficient and it is requested to find out an effective method for treating the disorders. On the other hand, none of the prior art including the above International Application and Japanese Patent Laid Open Publication teaches or suggests that interferon is effective for treatment of keratosic disorders of skin and mucosa.
One object of the present invention is to provide a stable interferon-containing pharmaceutical composition for treating keratosic disorders by topical or local application.
Another object of the present invention is to provide a novel method for treating keratosic disorders.
These objects as well as other objects and advantages of the present invention will become apparent to those skilled in the art from the following description.